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Myriophyllum farwellii — Farwell's water-milfoil

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Facts

Farwell's water-milfoil is named after its discoverer, the prominent American botanist Oliver Atkins Farwell (1868-1944). It is a native milfoil, and protected in some New England states.

Habitat

Lacustrine (in lakes or ponds), riverine (in rivers or streams)

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
aquatic
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf position
the leaves are all submerged underwater
Leaf arrangement
  • alternate: there is one leaf per node along the stem
  • whorled: there are three or more leaves per node along the stem
Leaf blade length
10–25 mm
Petal or sepal number
there are four petals, sepals, or tepals in the flower
Petal color
purple
Specific leaf type
the leaf is once pinnately divided and the segments are very narrow, each side providing the appearance of a comb
Floating leaf shape
NA
Fruit type (general)
the fruit is dry and splits open when ripe
Underwater leaf length
10–25 mm
Show all characteristics

  • Flowers

    Anther length
    0.4 mm
    Carpels fused
    the carpels are fused to one another
    Flower lower lip length
    0 mm
    Flower position
    the flowers are below the surface of the water
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Inflorescence type
    the flowers grow out of the axil (point where a branch or leaf is attached to the main stem)
    Length of flower stalk
    0 mm
    Length of peduncle
    0 mm
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    4
    Ovary position
    the sepals and/or petals are attached above the ovary
    Palate on corolla
    no
    Petal and sepal arrangement
    the flower includes two cycles of petal- or sepal-like structures
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal color
    purple
    Petal fringed edges
    the petals are fringed
    Petal fusion
    the perianth parts are separate
    Petal length
    1 mm
    Petal number
    4
    Petal or sepal number
    there are four petals, sepals, or tepals in the flower
    Pistil number
    1
    Sepal appearance
    the sepals resemble leaves in color and texture
    Sepal number
    4
    Spur length
    0 mm
    Stamen number
    4
    Stamens fused to petals
    the stamens are not fused to the petals or tepals
    Style number
    4

  • Fruits or seeds

    Fruit length
    2–2.5 mm
    Fruit type (general)
    the fruit is dry and splits open when ripe
    Fruit type (specific)
    the fruit is a schizocarp (when dry it splits into sections, each holding one or more seeds)
    Fruit width
    2 mm

  • Glands or sap

    Oil glands on nodes
    none of the nodes have oil glands
    Sap
    the sap is clear and watery

  • Growth form

    Lifespan
    the plant lives more than two years
    Root septa
    the roots do not have transverse septa
    Roots floating in water
    there are no clusters of roots floating in the water
    Turions
    the plant has turions
    Underground organs
    the plant has a rhizome (a horizontal underground stem with roots growing from it)

  • Leaves

    Bract position (Sparganium)
    NA
    Bract relative length
    At least 1379 mm
    Bracts
    the flowers or their pedicels have bracts at their bases
    Floating leaf basal lobes
    NA
    Floating leaf blade width
    0 mm
    Floating leaf length
    0 mm
    Floating leaf shape
    NA
    Floating leaf tip
    NA
    Floral bract form
    the bracts are much more lobed, or much less lobed, than the foliage leaves
    Floral bract length
    0.4 mm
    Leaf arrangement
    • alternate: there is one leaf per node along the stem
    • whorled: there are three or more leaves per node along the stem
    Leaf blade length
    10–25 mm
    Leaf blade veins
    the lateral veins radiate from the base and continue to spread away from the centerline of the leaf, or branch off the central vein at intervals
    Leaf position
    the leaves are all submerged underwater
    Leaf special features
    none of the mentioned special features are present
    Leaf-like branch segments
    5–12
    Leaf-like branch shape
    the leaf-like branches are round
    Specific leaf type
    the leaf is once pinnately divided and the segments are very narrow, each side providing the appearance of a comb
    Staminate bract edge (Myriophyllum)
    the edges of the staminate bracts are either smooth and without teeth, or with tiny, outward-pointing teeth
    Stipule appearance
    NA
    Stipule fused to leaf
    NA
    Stipules
    there are no stipules on the plant
    Stipules fused around stem
    NA
    Trap-bladder length
    0 mm
    Underwater leaf blade edges
    the underwater leaf blades are lobed
    Underwater leaf blade shape
    • the underwater leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    • the underwater leaf blade is triangular, with the stalk or attachment point on one of the sides
    Underwater leaf length
    10–25 mm
    Underwater leaf stalk
    yes
    Veins in floating leaf
    0

  • Place

    Habitat
    aquatic
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • in lakes or ponds
    • in rivers or streams

  • Stem, shoot, branch

    Flowering stem growth form
    the flowering stem is upright

Wetland status

Occurs only in wetlands. (Wetland indicator code: OBL)

In New England

Distribution

Connecticut
present
Maine
present
Massachusetts
present
New Hampshire
present, invasive, prohibited
Rhode Island
present
Vermont
present

Conservation status

Exact status definitions can vary from state to state. For details, please check with your state.

Massachusetts
extremely rare (S-rank: S1), endangered (code: E)
New Hampshire
unrankable (S-rank: SU), Ind (code: Ind)
Vermont
rare to uncommon (S-rank: S2S3)

From Flora Novae Angliae dichotomous key

3.  Myriophyllum farwellii Morong N

Farwell’s water-milfoil. CT, MA, ME, NH, RI, VT. Still or slow-moving, circumneutral to basic water of lakes and rivers.

Native to North America?

Yes

Sometimes confused with

Myriophyllum pinnatum:
flowers in emersed spikes, subtended by bract-like leaves, anthers 0.8–1.1 mm long, and fruits 1.3–1.8 mm long (vs. M. farwellii, with flowers in the axils of submersed leaves, anthers ca. 0.4 mm long, and fruits 2–2.5 mm long).
Myriophyllum humile:
leaves alternate or sometimes some leaves subopposite, especially in submersed plants), fruit 0.7–1.2 mm long, and mericarps rounded on the outer surface, without ridges or projections (vs. M. farwellii, with leaves typically both alternate and whorled on the same stem, fruit 1.3–2.5 mm long, and mericarps with 2 tuberculate, longitudinal ridges on the outer surface).

Family

Haloragaceae

Genus

Myriophyllum